Devices for the automatic recognition of authentic and forged documents measure light reflected by the documents or light transmitted through the documents by means of a predetermined number of photo-elements, whereby the documents are optically scanned only in individual predetermined points or in a determined grid of points. The documents are also illuminated by means of spectrally narrow light sources in order to recognize mechanically color differences at the surface of the documents, e.g. those of imprinted patterns (Great Britain Pat. Document 1,470,737).
A device known through DE-OS (German application) 29 47 958 is provided with a replaceable reading head which is equipped with a line-like arrangement of the photo elements and a linear illumination device attached on one side and integrated into the reading head, whereby white light is transmitted from a source outside the reading head by means of a light conducting bundle.
U.S. Pat. 3,872,434 shows an arrangement for the transformation of analog signals corresponding to a number of photo-elements utilizing a multiplexer and only one digital to analog converter. DE-OS (German application) 30 40 963 describes the evaluation of converted digital signals, the comparison with stored values and the identification of the document as well as the production of a signal for the control of a document sorting and conveying device.
It is the object of the instant invention to create a device for recognizing authentic documents with a reading head that is easily adaptable to the documents to be examined, and characterized by low cost, simple construction and which is easy to repair.